1. Field of the Invention
The present invention relates to an organic electroluminescent (hereinafter referred to as EL) display apparatus comprising organic EL elements which emit light when applied with electric charges.
2. Description of the Related Art
Typically, large display apparatuses comprising organic EL elements have a plurality of organic EL elements. Each EL element has an organic EL layer and a pair of electrodes for applying electric charges to this organic EL layer. The quantity of EL elements is determined in accordance with the number of pixels. The EL elements are formed on a single large substrate of an element to constitute a large screen panel, or, alternatively a small panels each having a predetermined number of organic EL elements formed thereon are stacked together to form a large panel.
The organic EL layer should be formed uniformly over the entire panel surface. In the case where a plurality of organic EL elements are formed on a single large substrate, therefore, it is difficult to form the organic EL layer uniformly over the entire substrate surface. Further, a non-uniformly formed organic EL layer would result in uneven brightness on the screen. In addition to a non-uniformly formed organic EL layer, brightness may occur when a hole carrying layer, an electron carrying layer, or electrodes are formed unevenly.
In the case where a plurality of small panels are stacked together to form a large panel, the organic EL layer of each panel can be formed uniformly so that uneven brightness can be suppressed when the large panel is formed. Since the individual electrodes of the organic EL element are very thin, about 1000 angstroms, however, the electrodes to be connected have narrow connecting faces. This makes it difficult to connect the associated electrodes of the adjoining small panels at their end portions.
Conventionally, only the electrodes are led out from each panel to connect the electrodes to thereby facilitate the connection of the panels. This method inevitably increases the joint portions which do not emit light making the joints prominently darker.